The present invention relates to a pressure controlled injector for high injection with a slider throttle.
An injection system for injection of fuel which is under high pressure into the combustion chambers of an internal combustion engine must nowadays satisfy, in addition to other requirements, the following requirements: An injection pressure and an injection quantity for each operation point of the internal combustion engine must be determined independently from one another, to obtain an additional freedom for the of mixture. The injection quantity at the beginning of the injection must be as small as possible to take into account the ignition drag between the beginning of the injection and the adjusted formation of the flame front in the combustion chamber. For obtaining a constant injection pressure for all cylinders of the internal combustion engine high pressure collecting chambers (common rail) are used which serve as a common fuel distributor. Very high pressure acts in these chambers, so that during opening an injector the injection pressure for all other injectors can be maintained constant.
The German patent document DE 197 21 879 A1 discloses a fuel injection device for internal combustion engines. It is provided with a high pressure collecting chamber (common rail) which is filled with fuel through by a high pressure pump. This high pressure collecting chamber is connected via injection lines with injection valves which extend into the combustion chamber of the internal combustion engine to be supplied. Its opening and closing movements are controlled correspondingly by an electrically controlled control valve. The control valve is formed as a 3/2 way valve and connects a high pressure line which opens to an injection opening of the injection valve, with an injection line or a relieve line or an unloading line. A hydraulic working chamber which is filled with fuel high pressure is provided on the control member of the control valve. It is controllable, for adjusting the adjusting position of the control valve member of the control valve in an unloading passage.
It is an object of the present invention to provide an improved pressure controlled injector for a high injection with a slider throttling.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in an injector of this type in which from a nozzle supply to a nozzle chamber, a permanently acting throttling element and a throttling element which is regulated by a valve body are branched off.
With the inventive solution it is possible in a simple manner to realize a pressure controlled injector for injection of fuel into the combustion chamber of an internal combustion engine. Actually in the inventive solution through throttle points are associated with the high pressure side nozzle supply to the nozzle chamber which surrounds the nozzle needle, with which the shutoff can be regulated. One of the throttle points to which high pressure is applied through the nozzle supply is placed so that, it is closed by a slider which is displaceable vertically in the injector housing and can be opened by it, while a throttle point located underneath is positioned relative to the slider so that it is loaded permanently with high pressure. Since the first mentioned throttle point is located so that it can be closed or open by overlapping of the slider and the control edge in the injector housing, it is accessible for a regulation by controlling a piezo actuator.
With the inventive solution a fast closing of the nozzle needle in its seat is obtained, so that the fuel quantity injected for the beginning of the preinjection remains low and so that adjusting ignition drag can be taken into consideration. Depending on the desired injection end, it is possible by controlling the slider-side throttle element to provide an outflow of a greater quantity of fuel which is under high pressure from the nozzle supply through the further throttle point, so that the nozzle needle closes faster, so that the nozzle needle can close faster and can move back sealingly in its seat.
In addition to the throttle which is not closeable by the slider and therefore operates permanently, the further controllable throttle point provides for a possibility of acting on the pressure unloading in the nozzle supply, to perform a fast closing of an injection nozzle. What was mentioned before with respect to the preinjection phase is applicable for main injection or post injection phases of the injector, during the injection of fuel into the combustion chamber of an internal combustion engine.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.